This invention relates to the treatment of textile fabrics containing cellulosic fibers to impart crease resistance, and in particular relates to an improved durable press fabric finishing process using aqueous formaldehyde,
Formaldehyde has long been recognized as a desirable finishing agent for fabrics containing cellulosic fibers. Formaldehyde is considerably lower in cost than the resin finishing agents currently used in most commercial durable press fabric finishing operations, and has enhanced durability. Additionally, unlike most resin-finished fabrics, formaldehyde-finished fabrics do not continue to liberate formaldehyde in storage, after initial removal.
However, despite widespread recognition of the desirable properties of formaldehyde and active scientific investigation for many years, as evidenced by numerous patents and publications describing finishing processes using aqueous formaldehyde, none of the processes heretofore known which use aqueous formaldehyde have been found suitable for routine application on a commercial scale. One of the principal factors limiting the commercial use of aqueous formaldehyde is the non-reproducibility of the finishing process in commercial applications. Traditional pad-dry-cure processes using aqueous formaldehyde have been found to be extremely variable and non-reproducible when practiced on a commercial scale. Unacceptable loss of fabric strength has also been observed in many of the proposed aqueous formaldehyde treatment processes.
Because of the aforementioned failings of prior aqueous formaldehyde processes, there have been continuing efforts to develop a suitable finishing process utilizing formaldehyde. One method which has been actively investigated and described in numerous patents involves the treatment of fabrics with formaldehyde in the vapor phase. However, this vapor phase technology requires specialized processing equipment and exacting processing conditions. For these and other reasons, the vapor phase formaldehyde technology has found limited acceptance commercially.
More recently, the application of aqueous formaldehyde at low wet pickup levels has been investigated as a means for overcoming the aforementioned problems. It has been proposed to apply aqueous formaldehyde mixed with a sulfur dioxide catalyst to the fabric by printing with an engraved roll to obtain a low wet pickup on the order of 15-35 percent, with the fabric being thereafter heated and cured in a conventional manner. While this process shows improvement over the earlier aqueous formaldehyde processes, it has certain disadvantages and limitations. The engraved roll used for applying the finishing agent is costly, and is subject to wear during continued use, resulting in a variation in the amount of finishing agent applied to the fabric. Additionally, with the engraved roll, it is difficult to accurately adjust and control the wet pickup level when changing to a fabric of a different weight, construction or color. Also, problems are presented in controlling and containing the fumes of the gaseous sulfur dioxide catalyst.